George WeigelWater gardens treated with Bt products are not harmful to dogs that like to drink out of the pond.

Q: I have a small water garden and a couple of huge Leonberger dogs that like to drink out of it. We're seeing mosquito larvae in the pond even though we've got fish. Several products are considered "safe around pets and children" but they do not mention if the water will be safe to drink. Any idea on that?

A: Fish usually do a pretty good job keeping water gardens mosquito-free. They eat the eggs, larvae and pupae almost as fast as adult mosquitoes lay them -- assuming you've got enough fish to keep up with the demand.

If that's not doing the trick, look for products containing either Bacillus thuringiensis israelenis (Bt-i) or Bacillus sphaericus.

These are both bacterial larvicides that are narrowly targeted to mosquitoes. The U.S. Environmental Protection Agency says they pose no risk to people, pets and the environment (including dogs that ingest it in treated water).